Non-metallic load center for surface and recessed wall mounting

ABSTRACT

A non-metallic load center comprises an insulative, molded plastic enclosure consisting of a housing having integrally formed back and sidewalls and a separable cover. Reinforcing ribs, integrally molded with the housing sidewalls, provide structural rigidity, as well as affording mounting surfaces lying in a plane perpendicular to the open front of the housing. Additional ribs at each housing corner are pre-drilled to receive nails for securing the load center to a wall stud; the rib mounting surfaces bearing against the stud to provide a parallel, substantially flush relationship between the front and cover surface and the finished wall for recessed load center mounting. External tabs integrally formed with the housing facilitate surface mounting of the load center and can be readily broken off for recessed mounting.

United States Patent 1191 Morby et al.

[ NON-METALLIC LOAD CENTER FOR SURFACE AND RECESSED WALL MOUNTING [75] Inventors: John Alfred Morby, Bristol; Joseph Francis Rich, New Britain; George Henry Grade, Jr., Simsbury, all of Conn.

[73] Assignee: General Electric Comapny, New

York, NY.

6/1973 7 Schindler et al.... 174/58 [451 Feb. 4, 1975 Primary ExaminerJ. V. Truhe Assistant ExaminerDavid A. Tone 1 Attorney, Agent, or Firm-R. A. Cahill; P. L. Schlamp; F. L., Neuhauser [57] ABSTRACT A non-metallic load center comprises an insulative, molded plastic enclosure consisting of a housing having integrally formed back and sidewalls and a separable cover. Reinforcing ribs, integrally molded with the housing sidewalls, provide structural rigidity, as well as affording mounting surfaces lying in a plane perpendicular to the open front of the housing. Additional ribs at each housing corner are pre-drilled to receive nails for securing the load center to a wall stud; the rib mounting surfaces bearing against the stud to provide a parallel, substantially flush relationship between the front and cover surface and the finished wall for recessed load center mounting. External tabs integrally 2 Claims, 5 Drawing Figures PATENTED FEB 1 5 SHEET 2 OF 3 NON-METALLIC LOAD CENTER FOR SURFACE AND RECESSED WALL MOUNTING BACKGROUND OF THE INVENTION Heretofore, enclosures for electrical equipment, such as circuit breaker panelboards or load centers, have invariably been metallic. These metallic enclosures are manufactured in mass production from metal sheets in a succession of operations, including cutting, blanking, forming and welding, to create a box-like housing, which must then be painted. The enclosure covers are similarly produced in a succession of operations. A number of components, including component mounting and supporting elements, must then be assembled in the box-like housing. Since the metallic enclosure is electrically, conductive, insulators must be incorporated into the mounting of the various bus bars to the enclosure.

Recently, a non-metallic, molded plastic electrical equipment enclosure in the form of a circuit breaker panelboard or load center has been introduced in the market and offers numerous advantages over its metallic counterpart. The complete box-like housing can be created in a single molding operation, as can the cover. Painting is unnecessary, and the plastic can be readily tinted and the mold designed to create a surface finish which is esthetically pleasing. Moreover, mounting and supporting elements may be integrally formed with the enclosure, thus simplifying assembly. In this context, the assembly of separate insulating members is obviated since the enclosure itself is an excellent insulator. As a consequence, a molded plastic enclosure is cheaper to manufacture in mass production than a comparable metallic enclosure. Moreover, electricians have found a molded plastic enclosure more convenient to install and wire.

It is accordingly an object of the present invent to provide a non-metallic, molded plastic enclosure for electrical equipment.

An additional object of the invention is to provide a non-metallic enclosure of the above character having improved mounting provisions for installing the enclosure to an interior wall.

Still another object of the invention is to provide a molded plastic enclosure of the above character wherein the mounting provisions are integrally formed with the enclosure.

A further object is to provide a non-metallic enclosure of the above character wherein the mounting provisions are conducive to both surface mounting on and recessed mounting in an interior wall.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

SUMMARY OF THE INVENTION In accordance with the invention, there is provided a non-metallic molded plastic enclosure for electrical equipment, such as a panelboard or load center for circuit breakers, having integrally formed back and sidewalls in the configuration ofa box-like housing. A separable molded plastic cover adapted to the housing completes the enclosure. Mounting provisions integrally LII formed with the housing are susceptible to surface mounting of the enclosure to the face of a wall orre cessed mounting of the enclosure within the wall, as desired by the installer.

More specifically, the housing sidewalls terminate in a perimetrical lip circumscribing the open front of the housing; the lip telescopically interfitting with a corresponding perimetrical flange molded to and depending from the front wall of the cover pursuant to the application of the cover into closure relation with the housing. Reinforcing ribs integral with and extending exteriorly from at least two opposed housing sidewalls are adapted to provide mounting surfaces lying in a common plane perpendicular to the front wall of the cover when applied in closure relation to the housing. Molded corner ribs protruding exteriorly from the junctions of the sidewalls are provided with means accommodating fastening elements for securing the enclosure to the side surface ofa wall stud pursuant to the recessed mounting of the enclosure within the wall. The mounting surfaces of the reinforcing ribs bearing against the wall stud surface serve to automatically orient the cover front wall in substantially parallel, flush relationship to the finished wall of the enclosure installation site.

Further in accordance with the present invention, the enclosure is provided with laterally extending, exterior mounting tabs integrally formed with the housing to accommodate fastening elements for securing the enclosure to the surface of a finished wall. Since the external mounting tabs extend beyond the plane of the reinforcing rib mounting surfaces and in order to initially universally adapt the enclosure to both surface and recessed mounting, the tabs are provided with score lines located intermediate the plane of the rib mounting surfaces and the housing sidewalls. These score lines facilitate the breaking off of the tabs at a predetermined lo-' cation along their lengths in order that they do not interfere with the recessed mounting of the enclosure to a wall stud.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings on which:

FIG. 1 is a perspective view of a non-metallic enclosure for electrical equipment constructed in accordance with the invention to include a molded plastic, box-like housing and a separable molded plastic cover;

FIG. 2 is a plan view, partially broken away, illustrating recessed mounting of the housing in FIG. 1 in combination with an alternative cover construction;

FIG. 3 is a side elevational view of the housing and cover form of FIG. 1 illustrating surface mounting of the enclosure;

FIG. 4 is a side elevational view of the enclosure of FIG. 2 in recessed mounted relation to a wall stud; and

FIG. 5 is a sectional view taken along line 5-5 of FIG. 2.

Like reference numerals refer to corresponding parts throughout the several views in the drawing lines.

DETAILED DESCRIPTION A non-metallic enclosure for electrical equipment, constructed in accordance with the invention, is seen in FIG. 1 to include a molded plastic, box-shaped housing, generally indicated at 10, and a molded plastic cover, generally indicated at 12. The housing and cover are formed of a suitable plastic, preferably a thermoplastic material, such as phenylene-oxide thermoplastic marketed by General Electric under the trademark NORYL. The housing comprises a backwall 14 and four integral sidewalls 16, 17 18 and 19. Cover 12, like housing 10, is formed in a single molding operation to include a front wall 21 and shallow sidewalls in the form of a perimetrical flange 22.

The housing sidewalls terminate in a perimetrical lip 24 surrounding the open front of housing 10. Adjacent the base of lip 24, the housing sidewall thickness is reduced to provide an outer ledge 26 circumscribing the outside perimeter of housing 10 and an inner ledge 28 circumscribing the inner perimeter; both of the ledges being in equally recessed relation to the open front of housing 10.

Referring to FIGS. 1 and 3, cover 12 is mounted to housing 10 by forming a pair of openings 30 in the upper horizontal portion of perimetrical flange 22 which receive upstanding, pyramidal-shaped hooks 32 integrally formed with the upper portion of housing lip 24. As best seen in FIG. 3, with hooks 32 engaged in openings 30 cover 12 is pivoted downwardly on housing 10 with lip 24 telescopically received within cover flange 22. To hold cover 12 in place, a screw 34 passes through an aperture 35 in the cover front wall 21 and into threaded engagement with a hole 36 formed in an equipment ground bus 38 mounted within housing 10. As seen in FIG. 1, the front wall 21 of cover 12 is molded to provide a row of knockouts 40 which are selectively removed to provide apertures accommodating the protrusion, with the cover in place, of the digitally operative portion of circuit breakers installed in housing 10, one being shown so installed at 42. The backwall and sidewalls of housing 10 are also molded to provide a series of conveniently located knockouts 44 which are selectively removed to accommodate introduction of cable during wiring installation of the enclosure.

The housing cover form seen in FIGS. 1 and 3 is utilized for those installations where the enclosure is to be surface mounted to a wall. To facilitate surface mounting, exterior mounting tabs 46 are integrally formed with three of the four housing sidewalls. Each tab is provided with an aperture 46a through which a nail 48 (FIG. 3) or other suitable fastening element may be driven into a wall 50 to, in effect, hang the enclosure thereto. It will be appreciated that the number of such mounting tabs 46 and their locations along the housing sidewalls at their junctions with the backwall 14 is strictly a matter of design and in no way limiting of the invention. Each of the mounting tabs is formed having a score line or groove 52 adjacent the junction of the individual tab with the housing sidewall to facilitate their being broken off by a pliers so as not to interfere with the recessed mounting of the enclosure within a wall at the site of installation. The structure of housing 10 lending to recessed mounting of the enclosure will now be described.

As seen in FIG. 1, each corner of housing 10 is formed with a rib 60 which is relatively large in cross section at its end terminating at the outer ledge 26 and tapers down to a smaller cross section at its other end adjacent the housing backwall 14. Not only does the cross section of ribs 60 decrease going from the ledge 26 toward the housing backwall 14, but also, as seen in FIG. 4, it also tapers inwardly toward the corner of the sidewalls and the backwall. This tapering of the corner ribs is for the purpose of facilitating release'of the hous- 5 ing from the mold cavity during manufacture. While the corner ribs 60 provide a measure of reinforcement, their principal function is to provide sufficient material to accommodate the drilling of a nail hole 62 adjacent its end of larger cross section. These nail holes 62 are pre-drilled at an angle of approximately from each sidewall to accommodate the passage of a nail 64 (FIGS. 2 and 4) for toe-nailing into the side of a wall stud, indicated at 66, pursuant to recessed mounting-of the enclosure within a wall.

In order to insure proper recessed mounting of the enclosure wherein the open front of the housing is substantially squared with the side surface of the wall stud 66 and consequently parallel to the finished wall, a pair of reinforcing ribs 68 integrally formed with each of opposed housing sidewalls 17 and 19 are provided intermediate the corner ribs 60. As best seen in FIG. 3, each rib 68 is of relatively narrow width and is further tapered such that its width adjacent lip 24 is somewhat greater than its width adjacent housing backwall 14. By virtue of their relatively narrow, tapered width, the faces 68a of the ribs common to a housing sidewall can be made to lie in a plane substantially perpendicular to the open face of housing 12 and still afford facile release from the mold cavity. The faces of these ribs 68 thus provide bearing surfaces which abut against the side of the wall stud 66, as seen in FIG. 5, when the enclosure is nailed in place to automatically orient the open front of the housing 10 in substantially parallel relation to the finished surface of wall 50. Also, as seen in FIG. 2, the outer ends of corner ribs 60 also provide face surface portions lying in the plane of rib mounting faces 68a to also bear against the stud 66. These additional bearings surfaces, though not necessary to insure squared recessed mounting, do provide backing adjacent nail holes 62 to reduce the possibility of damaging or disorienting the enclosure during toe-nailing to the wall stud.

When the housing 10 is recess mounted, as illustrated in FIGS. 2 and 4, a different cover form than cover 12 is used to complete the enclosure. This cover, generally indicated at 70, is integrally formed having a front wall 72 somewhat dimensionally larger than the open front of housing 12. A perimetrical flange 74 is integrally formed to depend from the back side of front wall 72 with each side thereof in set back relation to the corresponding edge of the cover front wall. The flange 74 is so located and dimensioned so as to telescopically fit within housing lip 24 when cover 70 is adapted to housing 10. The inside, rather than the outside, fit of flange 74 to lip 24 is necessary in order to avoid having to incorporate notches or reliefs in the cover flange to avoid interference with hooks 32 used in mounting cover 12 (FIG. 1). As seen in FIGS. 4 and 5, the overhanging edges of cover front wall 72 beyond flange 74 conveniently overlap the finished wall when cover 70 is mounted to housing 12, thus providing a neat and esthetically pleasing enclosure installation. It is noted from FIG. 4 that mounting tab 46 is removed along score line or groove 52 so as not to interfere with stud 66 during recessed mounting of the enclosure. To secure cover 70 in place, two screws are used, rather than one in the case of cover 12. Screw 34 passes through hole 35 in front wall 72 into threaded engagement with hole 36 in bus 38 (FIG. 1) while a second screw (not shown) passes through a hole into threaded engagement with a mounting post 80 (FIG. 2) integrally formed with sidewall 16 and backwall 14. The outer portion of post 80 is set back from lip 24 so as not to interfere with cover flange 74 upon mounting cover 70 in closure relation to housing 10.

From the foregoing description, it is seen that the present invention affords an improved non-metallic enclosure housing construction universally designed for both surface mounting on and recessed mounting in a wall. This dual adaptability significantly reduces manufacturing costs, simplifies production and lessens inventory expense as compared to a situation where different housing constructions are required for the two manners of enclosure installation. Moreover, the housing construction of the invention lends itself to convenient and expeditious on-slte installation by electricians.

It will thus be seen that the objects set forth above, among those made apparent in the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described our invention, what we claim as new and desire to secure by Letters Patent is:

1. An enclosure for electrical equipment comprising, in combination:

A. A molded, electrically insulative housing including a backwall and integrally formed, upstanding sidewalls,

1. said sidewalls terminating in a perimetrical lip circumscribing the open front of said housing,

B. A molded cover having 1. a front wall, and

pendicular relation to said front wall;

3. said flange and lip arranged to telescopically interfit upon application of said cover to said housing in closure relation to the open front thereof;

C. a pair of spaced reinforcing ribs integrally formed with each of an opposed pair of said sidewalls and extending between said lip and said backwall, said ribs being formed to provide mounting surfaces lying in a common plane perpendicular to said front wall of said cover when applied in closure relation to said housing;

D. corner ribs integrally formed with said housing and extending exteriorly from each junction of said sidewalls, each said pair of reinforcing ribs located intermediate said corner ribs;

E. mounting means formed in each said corner rib to facilitate recessed mounting said enclosure to a wall stud,

1. whereby upon mounting said enclosure, said mounting surfaces bear against the side of the wall stud to orient said cover front wall in substantially parallel, flush relation to a finished wall; and

' F. at least one mounting tab integrally formed with one of said sidewalls and extending exteriorly therefrom at a location adjacent said reinforcing ribs, said mounting tab facilitating mounting said enclosure to the surface of a wall.

2. The enclosure defined in claim 1, wherein said mounting tab extends exteriorly beyond said plane of said mounting surfaces, said mounting tab being formed with a score line located interiorly of said plane of said mounting surfaces, whereby said tab may be broken off along said score line so as not to interfere with recessed mounting of said enclosure. 

1. An enclosure for electrical equipment comprising, in combination: A. A molded, electrically insulative housing including a backwall and integrally formed, upstanding sidewalls,
 1. said sidewalls terminating in a perimetrical lip circumscribing the open front of said housing, B. A molded cover having
 1. a front wall, and
 2. a perimetrical flange integrally formed in perpendicular relation to said front wall;
 3. said flange and lip arranged to telescopically interfit upon application of said cover to said housing in closure relation to the open front thereof; C. a pair of spaced reinforcing ribs integrally formed with each of an opposed pair of said sidewalls and extending between said lip and said backwall, said ribs being formed to provide mounting surfaces lying in a common plane perpendicular to said front wall of said cover when applied in closure relation to said housing; D. corner ribs integrally formed with said housing and extending exteriorly from each junction of said sidewalls, each said pair of reinforcing ribs located intermediate said corner ribs; E. mounting means formed in each said corner rib to facilitate recessed mounting said enclosure to a wall stud,
 1. whereby upon mounting said enclosure, said mounting surfaces bear against the side of the wall stud to orient said cover front wall in substantially parallel, flush relation to a finished wall; and F. at least one mounting tab integrally formed with one of said sidewalls and extending exteriorly therefrom at a location adjacent said reinforcing ribs, said mounting tab facilitating mounting said enclosure to the surface of a wall.
 2. The enclosure defined in claim 1, wherein said mounting tab extends exteriorly beyond said plane of said mounting surfaces, said mounting tab being formed with a score line located interiorly of said plane of said mounting surfaces, whereby said tab may be broken off along said score line so as not to interfere with recessed mounting of said enclosure.
 2. a perimetrical flange integrally formed in perpendicular relation to said front wall;
 3. said flange and lip arranged to telescopically interfit upon application of said cover to said housing in closure relation to the open front thereof; C. a pair of spaced reinforcing ribs integrally formed with each of an opposed pair of said sidewalls and extending between said lip and said backwall, said ribs being formed to provide mounting surfaces lying in a common plane perpendicular to said front wall of said cover when applied in closure relation to said housing; D. corner ribs integrally formed with said housing and extending exteriorly from each junction of said sidewalls, each said pair of reinforcing ribs located intermediate said corner ribs; E. mounting means formed in each said corner rib to facilitate recessed mounting said enclosure to a wall stud, 